section the freezing point of water 3 - pearson … salt, on the freezing point of water. page of 2...

3SECTION

The freezing point of water

© Pearson Education Ltd 2009. Longman 11-14 Chemistry Practical and Assessment Teacher Pack This document may have been altered from the original

PRACTICAL

You are going to investigate the effect of dissolving different amounts of sodium chloride, common salt, on the freezing point of water.

Page of 21

• 25 cm3 measuring cylinder

• spatula

• stirring rod

• thermometer

• test tube

• crushed ice

• salt

• water

• access to an electronic balance

Apparatus (per group) • 250 cm3 beaker

Safety Avoid getting salt into your eyes.

Recording your results 1 Make a suitable table to record all your results. The independent variable should be

recorded in the first column and the dependent variable in the second column. Remember to include appropriate units in the column headings.

2 Plot a graph of temperature (°C) against mass of salt added (g). Draw a line of best fit.

Method 1 Use the measuring cylinder to add 25 cm3 of water to the beaker. 2 Add enough crushed ice so that the beaker is about half full. Stir the ice and water

with the stirring rod (do not use the thermometer to do this). 3 Measure and record the temperature of the ice/water mixture. 4 Add 2 g of salt to the mixture and stir with the stirring rod. 5 Measure and record the temperature of the mixture. 6 Repeat steps 4 and 5 until you have added a total of 10 g of salt.

7 Put approximately 2 cm3 of water in a test tube. Put the test tube into the mixture in the beaker. Observe and record what happens to water in the test tube.

3 The freezing point of water


4 Use your graph to predict the temperature you would have obtained if you had added 5 g and 7 g of salt in your experiment. What temperature might you have obtained if you had added 20 g of salt?

5 The accepted value for the freezing point of water is 0 °C. What temperature did you record in step 3 in the method (before you added any salt)? How close to the accepted value for the freezing point of water is this?

6 Explain what happened to the water in the test tube at the end of the investigation. Include ideas from the particle theory in your explanation.

7 Ice cream can be made from a mixture of milk, cream and sugar using a cooling bath containing ice, water and salt. Suggest why this works.

Evaluation 8 Identify any anomalous results in your investigation, and whether they appeared to be

too low or too high. 9 Suggest a reason for anomalous results in this investigation (even if you did not have

any). 10 Compare your results with the results obtained from other groups. How reliable were

your results? Suggest reasons for any differences between the sets of results. 11 All groups should have obtained the same temperature for the ice/water mixture at the

start of the investigation (0 °C if pure ice and water was used). Suggest a reason for any differences observed.

Considering your results/conclusion 3 Describe any pattern shown by your results. Does the temperature of the mixture in

the beaker change as the mass of salt added increases? If so, in what way?

Page of 22

3SECTION

Treating water


PRACTICAL

You are going to make a simple filtration unit to remove insoluble contaminants from water.

Apparatus (per group) • plastic drinks bottle, top half

• sand

• cotton wool

• small stones or gravel

• stand, boss and clamp

• 2 × 100 cm3 beakers

• evaporating basin

• muddy water

Method 1 Clamp the drinks bottle upside down by its neck.

2 Gently pack the neck with cotton wool. Make a filter bed by adding some sand

followed by a layer of small stones. Measure and record the depth of the sand layer. 3 Put a beaker under the neck of the drinks bottle, and add clean tap water to the top of

the filter bed. Repeat until the filtrate runs clear, then pour it away. 4 Put the evaporating basin under the neck of the drinks bottle. Mix some soil and water

together, and then pour it into the filter bed. 5 Collect the filtrate in the evaporating basin. Observe and record its appearance. 6 Leave the evaporating basin aside for several days to allow the water to evaporate.

Observe and record the appearance of any residue left behind in the basin.

Safety Do not drink the water from the filter.

stones

sand

cotton wool

Page of 21

3 Treating water


Considering your results/conclusion 2 Consider the appearance of the filtrate from the muddy water. Was it clear and

colourless? 3 Why might the filtrate be cloudy? 4 Why might the filtrate be coloured? 5 Consider the appearance of the residue after the water was evaporated from the

filtrate. Could you see any individual pieces of material? Was the residue coloured or colourless?

6 Why might the residue contain individual pieces of material? 7 Why might the residue be coloured? 8 To what extent was your filter bed successful at treating the muddy water?

Evaluation 9 What was the purpose of the cotton wool? 10 Why did you run tap water through the filter bed first? 11 Compare your results with the results obtained from other groups. Did the depth of the

sand bed make any difference to success of the filter bed? Suggest reasons for any differences in the success of the filter beds.

12 Why would the filtered water still not be safe to drink? 13 Describe how water at a water treatment works would be made safe to drink after

filtering it.

Recording your results 1 Make a suitable table to record all your results. You will be recording the depth of the

sand layer, and the appearance of the filtrate before and after evaporating the water.

Page of 22

3SECTION

pH testing – part one


PRACTICAL

In the first part of the experiment you are going to make an indicator solution from red cabbage. In part two, you will test various substances with your indicator (and also with litmus and universal indicator).

Page of 31

Safety Wear eye protection. Take care when cutting up the red cabbage. Take care when handling hot water.

Apparatus (per group) • chopping board and knife

• pestle and mortar

• filter funnel

• filter paper

• conical flask

• red cabbage

• sand

• hot water

Method 1 Carefully cut some red cabbage leaves into small pieces. 2 Transfer the pieces of red cabbage to the mortar. Add a little sand and hot water. 3 Use the pestle to grind the pieces of red cabbage so you get as much colour out of

the leaves as you can. 4 Set up a conical flask, filter paper and funnel.

5 Filter the mixture, collecting the filtrate in the conical flask. This is your red cabbage

indicator.

3SECTION

pH testing – part two


PRACTICAL

You are going to test various substances with different indicators.

Page of 32

Safety Wear eye protection. Do not taste any of the test substances. If you spill any of them on your clothing or skin, remove the contaminated clothing and wash the skin with plenty of water.

Apparatus (per group) • spotting tile

• glass rod

• dropping pipette

• universal indicator paper

• universal indicator pH colour chart

• red litmus paper and blue litmus paper

• red cabbage indicator (prepared in part one)

• substances to test

Method You may wish to carry out these tests, using water as the first test substance. 6 Add a few drops of cabbage indicator to a well in the spotting tile. Add a few drops of

the test substance and record the colour obtained. Wash out the dropping pipette.

7 Onto a clean part of the spotting tile, put a piece of universal indicator paper, a piece

of red litmus paper, and a piece of blue litmus paper. 8 Rinse the glass rod with water and then dip it into one of the test substances. 9 Touch the glass rod against each of the three indicator papers in turn so that a small

spot of liquid is transferred to each one. Try to avoid adding so much liquid that the colour runs out of the paper.

10 After about 30 seconds, record the colour of the spots on each indicator paper. Match the colour of the universal indicator paper spot to a colour on the colour chart, and record the corresponding pH value.

11 Repeat steps 6 to 10 with the remaining test substances. If you are unsure about any of the observations, repeat the test again for that substance.

3 pH testing


Recording your results 1 Make a suitable table to record all your results. The table below shows some

suggested headings.

Substance Colour

with red cabbage

Colour with red litmus

Colour with blue litmus

Colour with universal indicator

pH

Considering your results/conclusion 2 List the different test substances in pH order, from the lowest pH to the highest pH. 3 Identify any neutral substances from your results. What colour does each of the four

indicators have when neutral substances are added to them? 4 Identify the most acidic substance from your results. What colour does each of the

indicators have when strongly acidic substances are added to them? 5 Identify the most alkaline substance from your results. What colour does each of the

indicators have when strongly alkaline substances are added to them? 6 Copy and complete this table to summarise the colours seen with litmus paper:

Type of substance

Colour with red litmus

Colour with blue litmus

acidic

neutral

alkaline

Evaluation 7 Describe any difficulties you might have experienced carrying out this experiment. 8 Did you have to repeat any of the tests? If so, explain why you did this. 9 Compare your results with those obtained by other groups. How reliable were your

results? Suggest reasons for any differences between the sets of results. 10 Blue litmus paper stays blue with a certain substance. Explain why you cannot be sure

that the substance is alkaline, and how you could confirm whether or not it is alkaline using litmus paper.

11 Compare universal indicator paper with red and blue litmus papers and red cabbage indicator. Discuss the advantages and disadvantages of using each type of indicator paper.

Page of 33

3SECTION

Testing vinegar


PRACTICAL

You are going to use titration to find out which sample of vinegar contains the most acid.

Page of 21

Safety Wear eye protection. Vinegar forms an irritating vapour with a sharp smell. Dilute sodium hydroxide is an irritant. Avoid getting phenolphthalein on your skin. The burette is a long piece of apparatus. Do not over-reach to fill it – put the burette and its stand on a flat lab stool or on the floor to fill it if you cannot reach the top easily.

Apparatus (per group) • burette and stand

• white tile

• 25 cm3 measuring cylinder

• 250 cm3 conical flask

• 2 × 100 cm3 beakers

• dropping pipette

• filter funnel

• vinegar samples A and B

• sodium hydroxide solution

• phenolphthalein indicator

Method – part one 1 Clamp the burette firmly. Make sure the burette is vertical with

the tap at the bottom. Turn the tap so that it is off (turn to the horizontal position).

2 Put the white tile on the base of the burette stand – then put a beaker on the white tile.

3 Half-fill another beaker with water and pour this into the burette. Open the tap (turn it to the vertical position) and let the water run out. This cleans the burette.

4 Close the tap. Add some of one of the vinegar samples to the burette using the funnel, and then open the tap to run this waste into the beaker. Close the tap and then top up with vinegar to just below the 0.0 cm3 mark.

5 Measure 25 cm3 of the sodium hydroxide solution and pour this into the conical flask. Add a few drops of phenolphthalein indicator.

6 Put the conical flask under the burette, adjusting the height of the burette if needed.

7 Record the start burette reading. Open the tap a little. As the vinegar runs into the conical flask, gently swirl the flask to keep the liquids mixed. As soon as a permanent purple tinge appears, close the tap again. Record the end burette reading.

3 Testing vinegar


Page of 22

Method – part two 8 Empty the flask and wash it out. Repeat steps 5 to 7. 9 Open the tap to run the remaining vinegar into the flask. Empty the flask and wash it. 10 Repeat steps 3 to 8 with the other vinegar sample.

Considering your results/conclusion 2 The ‘titre’ is the volume of acid needed to neutralise the alkali – it is the difference

in cm3 between the burette reading at the end and the burette reading at the start. Calculate the mean titre for each vinegar sample.

Recording your results 1 Make a suitable table to record all your results. The table below shows some

suggested headings.

Vinegar A (run 1)

Vinegar A (run 2)

Vinegar B (run 1)

Vinegar B (run 2)

End burette reading (cm3)

Start burette reading (cm3)

The ‘titre’ – end reading minus start reading (cm3)

3 The weaker the vinegar, the greater the volume needed to neutralise the sodium hydroxide solution. Which sample of vinegar, A or B, is the weakest? How do you know?

Evaluation 4 Describe any difficulties you experienced carrying out this experiment. 5 How close to each other are the titres from run 1 and run 2 for each vinegar sample?

Suggest why the two titres might be different from each other, when they ought to be the same.

6 How confident are you that you have identified the weaker vinegar sample? Give reasons for your answer.

7 Compare your results with the results obtained by other groups. How reliable were your results? Suggest reasons for any differences between the sets of results.

3SECTION

Making copper sulphate


PRACTICAL

You are going to make dry copper sulphate crystals from copper oxide and sulphuric acid.

Page of 21

Safety Wear eye protection. Take care when handling hot water and hot sulphuric acid. Dilute sulphuric acid is an irritant. If you spill any on your clothing or skin, remove the contaminated clothing and wash the skin with plenty of water. Copper oxide is harmful. Avoid contact with your skin. Copper sulphate is harmful if swallowed. It is an irritant if it gets into your eyes.

Apparatus (per group) • 2 × 250 cm3 beakers

• boiling tube

• test tube rack

• test tube holder

• spatula

• filter paper

• filter funnel

• stand, boss and clamp

• evaporating basin

• dilute sulphuric acid

• copper oxide powder

• access to a kettle

• access to an electronic balance

7 Add the last quarter of copper oxide powder to the boiling tube. Lift the boiling tube from the water and gently shake it from side to side. Repeat the shaking from time to time over the next five minutes. The mixture will not go clear this time.

1 Add 15 cm3 of sulphuric acid to a boiling tube supported in a test tube rack.

2 Half-fill a 250 cm3 beaker with near boiling water from a kettle. Put the boiling tube from step 1 into the beaker of hot water.

3 Weigh out approximately 2 g of copper oxide powder onto a small piece of paper. Use the spatula to divide the powder into four quarters on the paper.

4 Carefully add one quarter of the copper oxide powder to the boiling tube of sulphuric acid. Lift the boiling tube from the water and gently shake it from side to side.

5 Allow time for the mixture to turn clear rather than cloudy – then repeat step 4. 6 Prepare another beaker half-filled with near boiling water from the kettle. Transfer the

boiling tube to this beaker of hot water and repeat step 4.

Method – part one

3 Making copper sulphate


Method – part two 8 Fold a piece of filter paper and put it into a filter funnel. Clamp the filter funnel over the

evaporating basin. 9 Use a test tube holder to hold the boiling tube by its neck, and pour the contents into

the filter funnel. 10 Collect the filtrate in the evaporating basin. Record the appearance of the residue in

the filter paper and of the filtrate. 11 Put the evaporating basin aside for a few days to allow the water to evaporate.

Inspect the crystals of copper sulphate formed and record your observations.

Considering your results/conclusion 2 Write a word equation for the reaction between sulphuric acid and copper oxide. 3 Why did you need to heat the sulphuric acid? 4 Why did you use a hot water bath, rather than heating the acid with a Bunsen flame? 5 Copper oxide is insoluble in water. Suggest why the copper oxide powder disappeared

at first when added to the sulphuric acid, but later some of it remained undissolved. Why was it important to make sure that extra (excess) copper oxide was added to the acid?

6 Why was the reaction mixture filtered? 7 Identify the residue in the filter paper and the filtrate in the evaporating basin.

Evaluation 8 Describe any difficulties you experienced carrying out this experiment. 9 Compare the quality and appearance of your crystals with those obtained by other

groups. Suggest reasons for any differences observed. 10 Your teacher said that you should have made just over 7.0 g of copper sulphate

crystals. Suggest why you have made less than 7.0 g of crystals.

Recording your results 1 Make a suitable table to record your observations during the investigation, such as:

• what happens when the copper oxide powder is added to hot sulphuric acid

• the appearance of the residue in the filter paper

• the appearance of the filtrate in the evaporating basin

• the appearance of the copper sulphate crystals.

Page of 22

3SECTION

Acid rain


PRACTICAL

Sulphur dioxide is one of the gases that causes acid rain. You are going to investigate its effects on seeds and building materials.

Apparatus (per group) • 2 plastic containers with close-fitting lids

• 2 dropper pipettes

• 2 Petri dishes with lids

• cotton wool

• cress seeds

• various substances to test

• sodium metabisulphite solution

• magnifying glass

Safety Wear eye protection.

Sodium metabisulphite solution smells because it releases small amounts of sulphur dioxide. This is a toxic gas with a choking sharp smell. It might cause an asthma attack if you suffer from asthma. Only use what you need, work with plenty of ventilation and do not breathe in over the solution.

Method – part one 1 Line two Petri dish lids with a shallow layer of cotton wool. Add some tap water to

dampen the cotton wool. Sprinkle an equal number of cress seeds over each layer of damp cotton wool. Put the completed Petri dish lids into the bottom of the plastic containers, one lid per container.

2 Collect two samples of each test substance as provided by your teacher. These will include small pieces of different metals, building materials and rocks. Aim to choose similar pieces of each test substance.

3 Use the magnifying glass to examine each test substance and a cress seed. Record your observations.

4 Arrange the test substances next to the Petri dish of cress seeds in the bottom of each plastic container. Leave space in each plastic container for a Petri dish bottom.

5 Line two Petri dish bottoms with a shallow layer of cotton wool.

6 Use a dropper pipette to add some water to one of the Petri dish bottoms. Put the Petri dish bottom in the bottom of one of the plastic containers. Carefully fit the lid to the plastic container and label it with your names and the date, and ‘no SO2’.

7 Repeat step 6 with the other Petri dish bottom and plastic container, but this time use the other dropper pipette to add the same volume of sodium metabisulphite solution. Label this plastic container with your names and the date, and ‘with SO2’.

8 Leave both plastic containers aside for a few days.

Page of 21

3 Acid rain


Method – part two 9 After a few days, open each plastic container to examine its contents. Open the

‘with SO2’ plastic container in the fume cupboard and leave its Petri dish of sodium metabisulphite solution in there. Use the magnifying glass to examine each test substance and the cress. Record your observations.

Recording your results 1 Make a suitable table to record your observations during the investigation. You will

need space to record the appearance of the test substances and cress:

• before adding them to the containers

• after leaving one of each in the container without sulphur dioxide

• after leaving one of each in the container with sulphur dioxide.

Considering your results/conclusion 2 What was the purpose of the sodium metabisulphite solution? 3 Why did you use one container with sodium metabisulphite and one with water? 4 Describe the differences observed in the development of the cress in the two

environments. What effect does the presence of sulphur dioxide have on the cress? 5 Describe the differences observed in the appearance of the metals in the two

environments. Were any of the metals damaged by the presence of sulphur dioxide? Did any of them appear to be not damaged by the presence of sulphur dioxide? Suggest a reason why this might be.

6 Describe the differences observed in the appearance of the plastic, rocks and building materials in the two environments. Were any of them damaged by the presence of sulphur dioxide? Did any of them not appear to be damaged by its presence?

7 Suggest which materials would be best suited to constructing buildings in heavily polluted environments. Explain your answer and outline any problems to builders that such a choice of materials might cause.

Evaluation 8 How reliable are your results? Compare your results with those obtained by other

groups, and suggest reasons for any differences observed. 9 How confident are you that you can draw firm conclusions from your experiment? 10 How would you improve the experiment, if you had to do it again? 11 Describe how you might extend the experiment.

Page of 22

3SECTION

The freezing point of water

Teacher and Technician sheet


PRACTICAL

Safety Sodium chloride presents a low hazard. Wear eye protection.

Resources (per group of pupils) Notes

250 cm3 beaker This can be glass or plastic.

25 cm3 measuring cylinder Pupils will be measuring out 25 cm3 of water.

spatula This is so that pupils can weigh out sodium chloride – it could be provided next to the balance rather than per group.

stirring rod

thermometer Provide alcohol thermometers rather than mercury thermometers. The minimum temperature reading should be −10 °C or lower.

test tube

crushed ice Each group needs about 100 cm3 of crushed ice.

sodium chloride Table salt can be used instead.

electronic balance The balance should read to a minimum precision of ±0.1 g. Two or more groups could share a balance.

de-ionised water Tap water would do instead.

Page of 11

3SECTION

Treating water



PRACTICAL

Safety Take care to avoid sharp edges when cutting the plastic drinks bottles in half.

Resources (per group of pupils) Notes plastic drinks bottle Use empty 2 litre plastic drinks bottles.

Cut each bottle in half around the middle. The pupils need the top half with the neck.

sand Use children’s play sand rather than builders’ sand.

cotton wool

small stones or gravel If possible, wash the gravel beforehand in a bucket of water.

stand, boss and clamp

2 × 100 cm3 beakers These may be glass or plastic.

evaporating basin

soil You may wish to put out old spoons with the soil so that the pupils can mix it with water.

Resources (per class) Notes Waste bin lined with a plastic bin sack The pupils will need to dispose of the

excess soil and their filter bed when finished. You may wish to return the muddy water to the ground outside, and to recycle the sand and gravel by washing it in buckets of water.

Page of 11

3SECTION

pH testing – part one



PRACTICAL

Resources (per group of pupils) Notes chopping board and knife Consider chopping the red cabbage

leaves before supplying them to the pupils to avoid using knives.

pestle and mortar

filter funnel

filter paper

conical flask 100 cm3 capacity would be suitable – or supply a boiling tube and test tube rack instead.

red cabbage

sand Optional – to improve the grinding of the red cabbage leaves.

kettle Bunsen burner, tripod, gauze and beaker can be provided instead.

Safety Low hazard presented.

Page of 21

3SECTION

pH testing – part two



PRACTICAL

Safety Eye protection must be worn when preparing the test substances. Dilute the household liquids as necessary to avoid exposing pupils to strongly acidic or alkaline solutions. Do not exceed 0.1 M for the laboratory acids and alkalis. Label each container so that pupils know the identities of the substances they are testing. Include appropriate hazard symbols – e.g. irritant for alkalis.

Resources (per group of pupils) Notes spotting tile A plain ceramic tile can be used instead.

glass rod

dropping pipette

universal indicator paper

universal indicator colour chart

red litmus paper

blue litmus paper

water, a range of household liquids, laboratory acids and alkalis

Select the substances so that pupils are able to record a range of pH values. Household substances might include: • bleach • lemon juice • oven cleaner • liquid soap • vinegar • washing powder • washing-up liquid Laboratory substances might include: • hydrochloric acid • sulphuric acid • ammonia solution • limewater • sodium hydroxide solution

Page of 21

3SECTION

Testing vinegar



PRACTICAL

Safety Ethanoic acid is corrosive. Wear eye protection (a face shield is best) and gloves and work with a fume cupboard when diluting concentrated ethanoic acid. Sodium hydroxide is corrosive. Wear eye protection (a face shield is best) and gloves and work with a fume cupboard when preparing aqueous sodium hydroxide.

Resources (per group of pupils) Notes burette and burette stand A stand, clamp and boss can be used

instead of a burette stand.

white tile

25 cm3 measuring cylinder

250 cm3 conical flask

2 × 100 cm3 beakers

dropping pipette

filter funnel

phenolphthalein indicator This is best supplied in a labelled dropping bottle.

vinegar sample A Prepare a 0.10 M solution of ethanoic acid (5.2 cm3 per dm3), or diluted white distilled vinegar (1 part vinegar to 9 parts water). Label it ‘Vinegar A’. Allow 75 cm3 per group. See the safety notes above.

vinegar sample B Prepare a 0.09 M solution of ethanoic acid (4.7 cm3 per dm3), or diluted white distilled vinegar (1 part vinegar to 10 parts water). Label it ‘Vinegar B’. Allow 75 cm3 per group. See the safety notes above.

0.075 M sodium hydroxide solution (3 g NaOH per dm3)

Label it as irritant. Allow 125 cm3 per group. See the safety notes above.

Page of 11

3SECTION

Making copper sulphate



PRACTICAL

Safety Eye protection must be worn when preparing the sulphuric acid. The copper(II) sulphate crystals produced in the investigation are an irritant if they get into the eyes. The crystals could be used to prepare copper(II) sulphate solutions for use in other practicals. Pupils must not be allowed to take the copper(II) sulphate crystals out of the lab.

Resources (per group of pupils) Notes

2 × 250 cm3 beakers

boiling tube

test tube rack

test tube holder

spatula

filter paper

filter funnel

stand, boss and clamp

evaporating basin

1.2 M sulphuric acid Label it as irritant. Allow 25 cm3 per group.

copper(II) oxide powder Label it as harmful. Allow 2.5 g per group.

kettle You may wish to provide one kettle between two or more groups of students.

electronic balance The balance should read to a minimum precision of ±0.1 g. Two or more groups could share a balance. You may wish to pre-weigh a 2 g portion of copper(II) oxide powder onto pieces of paper, or into small test tubes, for each group instead of giving pupils access to balances.

Page of 11

3SECTION

Acid rain



PRACTICAL

Page of 11

Safety Eye protection must be worn when preparing the aqueous sodium metabisulphite solution. 0.1 M sodium metabisulphite presents a low hazard, but inhalation of sulphur dioxide may exacerbate pre-existing breathing conditions such as asthma. Teachers should be aware of pupils who suffer from breathing problems because the smell of sulphur dioxide can be detected from the solution. The experiment takes two lessons. It would be advisable to have access to a fume cupboard.

Resources (per group of pupils) Notes 2 large plastic containers with airtight lids Tupperware® or similar.

2 dropping pipettes

2 Petri dishes with lids Each group needs four shallow dishes.

cotton wool

cress seeds

magnifying glass If you have sufficient numbers, allow one per pupil.

0.1 mol dm−3 sodium metabisulphite 19 g dm–3 sodium metabisulphite Na2S2O5. Allow 15 cm3 per group.

various substances to test The pupils are examining the effect of ‘acid rain’ on the cress seeds and various materials. These materials could include small pieces of: • metals (e.g. iron, steel, copper, zinc,

aluminium, magnesium) • plastic (e.g. PVC, polythene,

polystyrene) • rock (e.g. chalk, limestone, granite) • brick • concrete.

3SECTION

3.1 Our water supply


Questions 1 River water must be treated to make it ‘potable’, or safe to drink. Make a flow chart to

show how river water is treated after collecting it in a reservoir. There is no need to draw diagrams and you should use your own words. Start your flow chart like this:

[Total 6]

2 The table shows the different uses of potable water by people in the UK.

Use Litres per person per day Bath and shower 46

Dishwasher 8

Flushing toilet 36

Food preparation and drinking 5

Laundry 16

Other uses (garden, washing car etc.) 19 a) Draw an appropriate chart or graph to display the data in the table. [4] b) i) List any uses that definitely need potable water. Explain your answer. [2] ii) List any uses that do not necessarily need potable water. Explain your

answer. [2] iii) Are there any uses that could be met by untreated water but are actually

best met by potable water? Explain your answer. [2] c) Consider the stages involved in treating river water to make it potable.

i) Suggest which stage is likely to be the most costly and give your reasons. [2] ii) Apart from saving money, why might the government and water

companies want the public to reduce their consumption of water at home? [2] [Total 14]

Page of 11

3SECTION

3.2 Answers – not questions

Name Date Class


Acids, alkalis and neutralisation There are fifteen answers in the table below. Decide on suitable questions for each answer and write them in the table. Try your questions on a partner. Do they get the same answer as you started with? Discuss any similarities and differences with your partner.

Answers without questions

Answer Question

1 A neutralisation reaction

2 Changes colour in acids

3 Alkaline

4 Ammonia

5 Corrosive

6 H2SO4

7 Hydrochloric acid

8 Less than pH 7

9 Magnesium hydroxide

10 pH 7

11 Red litmus paper

12 The pH scale

13 Titration

14 Universal indicator

15 Use baking soda

Page of 11

3SECTION

3.3 Making salts


Cut out the jigsaw pieces and then use them to answer the questions below. You will need to use some pieces more than once. Some compounds need three pieces rather than just two.

Page of 11

Questions 1 a) Make these acids – hydrochloric acid (hydrogen chloride), nitric acid

(hydrogen nitrate), sulphuric acid (hydrogen sulphate). b) Make these alkalis – sodium hydroxide, potassium hydroxide, magnesium

hydroxide, calcium hydroxide. c) Make water (hydrogen hydroxide). [Total 8]

2 Choose one acid and one alkali. Write down their names, and then rearrange the pieces to form the salt and water. Write down the name of the salt, then the word equation for the reaction. Repeat with the other acids and alkalis (there are 12 combinations).

[Total 12]

Do not print this sheet double-sided

3SECTION

Chlorination of drinking water


HSW

Killing harmful microorganisms Chlorine gas has been used to disinfect drinking water in the UK for over 100 years. It reacts with water at the water treatment works to produce a mixture of chloric acid and hydrochloric acid. Harmful microorganisms are killed by chloric acid, but its concentration decreases as the pH increases. For example, its concentration at pH 7.5 is about nine times lower than its concentration at pH 6.5 (pure water is neutral at pH 7).

Most people can taste or smell chlorine in water when its concentration is as low as 5 mg per litre. Some people can even detect it when its concentration is just 0.3 mg per litre. Consumers complain when its concentration in drinking water rises above 0.6 mg per litre.

Chlorine reacts with compounds in water to form potentially hazardous substances, such as trichloromethane. There is experimental evidence that this can cause cancer in laboratory animals, but not enough evidence for it doing so in humans. Water companies take steps to minimise the amounts of such compounds in water and levels are constantly monitored. Scientists estimate that the risk of getting cancer from the by-products of chlorination is between a 100 and 1000 times less than the risk of dying from swallowing harmful microorganisms in untreated water.

Questions 1 a) Which acids are formed when chlorine dissolves in water? [2]

b) Name the acid responsible for killing microorganisms in water. [1] c) Suggest why the World Health Organisation (WHO) recommends that the pH

of drinking water should be less than 8. [1] d) Swimming pool water is kept at around pH 7.3 by adding sodium carbonate.

Suggest why a lower pH is not chosen, even though this would be better for killing harmful microorganisms. [1]

[Total 5] 2 a) Suggest why WHO recommends a minimum of 5 mg chlorine per litre in

drinking water. [1] b) About 0.5 mg chlorine per litre is added to water at UK water treatment plants. i) Explain why this amount might have been chosen. [1]

ii) Suggest why the actual concentration of chlorine in the water coming out of our taps may be lower than 0.2 mg per litre. [2]

c) Why is the concentration of chlorine in swimming pools around 3 mg per litre? [2] [Total 6]

3 Discuss the advantages and disadvantages of chlorinating drinking water. Why does it continue to be done when harmful substances are known to form as a result?

[Total 4]

Page of 11

3SECTION

Joseph Black and chalk


HSW

In 1755, Joseph Black reported on his experiments with chalk, an almost pure form of calcium carbonate. Read the information about his experiments and then answer the questions.

Experiment 1 Black weighed a piece of chalk, He then added a weighed amount of hydrochloric acid to it. He waited until the mixture stopped fizzing and weighed the mixture. He found that its mass was less than it had been before the reaction.

Experiment 2 Black took a piece of chalk that weighed the same as the first one. He heated it strongly and was left with a piece of white solid, called quicklime. He weighed the piece of quicklime. He found that it weighed less than the chalk had done. The loss in mass was the same as the loss in mass during Experiment 1.

Experiment 3 Black took the piece of quicklime from Experiment 2. He added to it the same weight of hydrochloric acid as he had used in Experiment 1. There was no fizzing or loss of mass.

Experiment 4 Black dissolved quicklime in water to make limewater. He found that a dish of this went cloudy during a church service attended by 1500 people, but not in the same empty church. Questions 1 a) Copy and complete these word equations:

i) calcium carbonate + hydrochloric acid → ______ + ______ + ______ [3]

ii) calcium carbonate → calcium oxide + ______________________ [1]

iii) calcium oxide + hydrochloric acid → _________ + _________ [2] b) Explain why improvements in weighing technology were important to Black’s

experiments with chalk. [1] c) What are the chemical names for chalk and quicklime? [2]

[Total 9] 2 a) Why did Black use identical masses of chalk in Experiments 1 and 2? [1]

b) Suggest why Black concluded that the loss of mass in Experiments 1 and 2 was caused by the loss of a gas. [2]

[Total 3] 3 a) Explain why the limewater went milky white during the church service. [2]

b) Why did Black repeat Experiment 4 in the empty church? [1] [Total 3]

Page of 11

3SECTION

Sulphuric acid


HSW

Read this extract from a newspaper article about sulphuric acid and answer the questions.

Sulphuric acid prices go mad Sulphuric acid prices have seen a huge increase in recent months after several years of decline. They have reached £200 per tonne six months after a low of just £50 per tonne. Several factors seem to be involved: the world price of sulphur is rising; there is an increased demand for sulphuric acid for fertiliser manufacture; and sulphuric acid itself is in short supply.

The UK Government’s Renewable Transport Fuel Obligation means that 5% of fuel must come from renewable sources by 2010. An increased demand for bioethanol to fuel cars has added to the demand for sulphuric acid. A typical bioethanol factory needs several thousand tonnes of the acid each year.

Page of 11

Questions 1 a) By how much did the price of sulphuric acid increase in six months? [1]

b) Give two uses of sulphuric acid mentioned in the article. [2] [Total 3]

2 a) Sulphuric acid is manufactured by the Contact Process. Copy and complete this word equation for the first stage in this process:

sulphur + _____________ → sulphur dioxide [1] b) Explain why the cost of sulphur would affect the cost of sulphuric acid. [1] c) Suggest why the cost of sulphur might increase. [2]

[Total 4] 3 In the UK, bioethanol is manufactured from sugar or wheat. Around 9 kg of sugar

beet must be grown for each litre of bioethanol produced. a) Suggest why an increase in the demand for bioethanol might cause an

increase in the demand for fertilisers. [1] b) Explain how the demand for fertilisers affects the demand for sulphuric acid. [2] c) Some people see a rising demand for bioethanol as a ‘double whammy’ for

the demand for sulphuric acid. They mean that bioethanol demand involves two factors that affect the demand for sulphuric acid. Identify these factors. [2]

[Total 5] 4 Used sulphuric acid can be recycled, but this is costly. Explain why recycling sulphuric

acid is becoming more attractive. What are the advantages and disadvantages of recycling sulphuric acid compared to manufacturing it from sulphur?

[Total 4]

EXTENSION3

SECTION

Symbol equations

© Pearson Education Ltd 2009. Longman 11-14 Chemistry Practical and Assessment Teacher Pack This document may have been altered from the original Page of 21

You are going to write symbol equations for some neutralisation reactions. Use the information below to help you to answer the questions.

Word equations Here are the general word equations for neutralisation reactions involving bases:

• acid + metal oxide → salt + water

• acid + metal hydroxide → salt + water

• acid + metal carbonate → salt + water + carbon dioxide

Symbol equations A word equation shows the reactants and products in a chemical reaction, but it is not quantitative. Word equations do not give information about the numbers of atoms and molecules involved. So chemists usually use symbol equations instead. In a symbol equation, there must be the same number of atoms of each element on both sides of the equation. If the number of atoms of one or more elements is not the same, the equation is not balanced.

For example, this equation is not balanced: HCl + CuO → CuCl2 + H2O The formulae are correct and cannot be changed, but there are two hydrogen atoms and two chlorine atoms on the right, and only one of each on the left. A number ‘2’ is put in front of the formula for HCl in the equation to balance it: 2HCl + CuO → CuCl2 + H2O

Chemical formulae The chemical formula of a substance shows the number of atoms of each element it contains. The table shows the formulae of some salts. The small numbers show how many atoms, or groups of atoms, there are in the compound. For example:

• in CuCl2 there is one copper atom and two chlorine atoms

• in Cu3(PO4)2 there are three copper atoms and two phosphate groups (PO4)

Name of salt Formula Name of salt Formula

copper chloride CuCl2 magnesium phosphate Mg3(PO4)2

copper nitrate Cu(NO3)2 magnesium sulphate MgSO4

copper phosphate Cu3(PO4)2 sodium chloride NaCl

copper sulphate CuSO4 sodium nitrate NaNO3

magnesium chloride MgCl2 sodium phosphate Na3PO4

magnesium nitrate Mg(NO3)2 sodium sulphate Na2SO4

3 Symbols equations


Questions 1 Copy the table below. Leave plenty of space in the empty boxes for names and

formulae. Complete your table by writing in the name and formula of the salt formed when each acid and base react with each other. One has been done for you.

Base

Acid sodium hydroxide NaOH copper

oxide CuO magnesium carbonate MgCO3

hydrochloric acid HCl magnesium

chloride MgCl2

nitric acid HNO3

sulphuric acid H2SO4

phosphoric acid H3PO4

[Total 11] 2 a) Write the word equations for the reactions in question 1. For example:

hydrochloric magnesium magnesium carbon acid + carbonate → chloride + water + dioxide

[11] b) Underneath each name in the word equations you have written in part a)

write the formulae of each compound. For example:

hydrochloric magnesium magnesium carbon acid + carbonate → chloride + water + dioxide HCl MgCO3 MgCl2 H2O CO2

[11] c) Complete the balanced symbol equation for each reaction, adding numbers if

needed. For example:

hydrochloric magnesium magnesium carbon acid + carbonate → chloride + water + dioxide 2HCl + MgCO3 → MgCl2 + H2O + CO2

[11] [Total 33]

Page of 22

3SECTION

The nature of acids


EXTENSION

Ideas about acids have changed over time. The table below shows some of the scientists who were involved and what they did. Use the information to help you answer the questions.

1 Henry Cavendish

(1731–1810)

In 1766, Cavendish was able to make ‘inflammable air’. This gas produced dew on the inside of its container when it was burned in air. He concluded that inflammable air produces water when it burns. 2

Joseph Priestley (1733–1804)

In 1772, Priestley added concentrated sulphuric acid to sodium chloride. The reaction made an acidic gas that he called ‘marine acid air’. In 1774, he heated mercury oxide. The reaction made mercury and a colourless gas that he called ‘dephlogisticated air’.

3 Carl Scheele (1742–1786)

In 1774, Scheele dissolved marine acid air in water to make ‘muriatic acid’. He added this acid to a mineral containing manganese dioxide. The reaction made a pale green-yellow gas that was later called ‘oxy-muriatic acid’.

4 Antoine Lavoisier

(1743–1794)

Lavoisier carried out lots of experiments, particularly those involving burning. In 1777, he reported that acids are made when sulphur, phosphorus or carbon burn and the products are dissolved in water. He named the gas in air that helps things to burn ‘oxygen’, meaning acid-former.

5 Humphry Davy (1778–1829)

In 1810, Davy showed that oxy-muriatic acid did not contain oxygen and could not be broken down. He discovered that muriatic acid contained hydrogen and one other element. He called this chlorine, from the Greek word for pale green.

6 Justus von Liebig

(1803–1873)

In 1838, Liebig suggested that acids are substances that contain hydrogen, and that this hydrogen is released when acids react with metals.

Page of 21

3 The nature of acids


Questions 1 a) Copy and correctly balance this symbol equation for Cavendish’s

‘inflammable air’ burning in air: _H2 + O2 → _H2O [1] b) What is the modern name for ‘inflammable air’? [1] c) i) Why did Cavendish think that water had been made in his experiment? [1]

ii) Describe a simple chemical test that Cavendish could have done to prove that water had been made. [2]

[Total 5] 2 a) What is the modern name for the gas produced by Priestley in 1774? [1] b) Here is the symbol equation for the experiment carried out by Scheele: MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 i) What is the modern name for ‘muriatic acid’? [1]

ii) The green-yellow gas was called ‘oxy-muriatic acid’. Did it contain oxygen as its name suggests? [1]

iii) Suggest why Priestley called the gas he made in 1772 ‘marine acid air’. [1] [Total 4]

3 Here are the formulae for acids made by Lavoisier: H2SO4, H3PO4 and H2CO3. a) To what extent do his experiments with sulphur, phosphorus and carbon

show that all acids contain oxygen? [1] b) i) Apart from oxygen, which element do all three acids have in common? [1]

ii) What compound is formed when this element burns in air? [1] iii) Suggest why Lavoisier might have been worried by Cavendish’s

experiment, and why he repeated it. [2] [Total 5]

4 a) Suggest why Scheele is given the credit for discovering chlorine, even though he did not realise the reaction with muriatic acid produced an element. [1]

b) Suggest how Lavoisier might have modified his theory of acids if he could have known the results of Davy’s experiments on ‘oxy-muriatic acid’. [2]

c) To what extent do the formulae of acids support Liebig’s suggestion that acids are substances that contain hydrogen? [1]

d) Cavendish thought that his ‘inflammable air’ came from the metals he used in his experiments with acids. Was he right? Explain your answer. [1]

e) Lavoisier gave hydrogen its name, meaning ‘water former’. Discuss whether you think he got the names for oxygen and hydrogen the wrong way round. [1]

[Total 6]

Page of 22

3SECTION

Questions and answers


Page of 11

What is the freezing point of pure water in degrees Celsius? 0 °C Why is chlorine added to drinking

water? To kill bacteria

Name a gas responsible for producing acid rain.

Sulphur dioxide or nitrogen dioxide

What happens when fertilisers run off fields into rivers and lakes?

Algae grow faster, oxygen is used up, fish die

What happens to the temperature of water as it boils? It stays the same

What colour change happens when water is added to dry cobalt chloride paper?

Blue to pink

What is the source of energy needed to drive the water cycle?

Heat from the Sun

How can we get pure water from sea water? Use distillation

Name the main salt in sea water. Sodium chloride What is the reaction between an acid and an alkali called? Neutralisation

If a substance has a pH of 7, what does that mean? It is neutral What does it mean if a substance

turns universal indicator paper red? The substance is strongly acidic

What do ammonia, toothpaste and baking powder have in common?

They are all alkalis

What will neutralise a wasp sting – vinegar or baking soda? Vinegar

What substances are formed when an acid and alkali react together? A salt and water What substances form when an

acid reacts with a metal oxide? A salt and water

What substances form when an acid reacts with a metal carbonate?

A salt, water and carbon dioxide

Name the salt formed when lithium hydroxide reacts with sulphuric acid.

Lithium sulphate

What acid should be used to make ammonium nitrate? Nitric acid Describe a test for carbon dioxide. Limewater turns

cloudy

Name the gas produced when magnesium reacts with hydrochloric acid.

Hydrogen What is the chemical formula of sulphuric acid? H2SO4

Describe a simple laboratory test for hydrogen.

A lighted splint makes hydrogen go ‘pop’

Name the industrial process used to make sulphuric acid.

The Contact Process

If a substance has a pH of 10, what does that mean?

It is weakly alkaline

What do we call a base that dissolves in water? An alkali

What happens to the pH of hydrochloric acid when it is diluted with water?

It goes up Name the acid in the stomach. Hydrochloric acid

What is the formula of water and what does it tell us about the water molecule?

H2O – it contains two hydrogen atoms and one oxygen atom

Why are marble statues more affected by acid rain than granite ones?

Marble contains calcium carbonate which reacts with acids; granite does not

PROGRESSION3

SECTION

Water and solutions

Name Date Class


Tick the boxes that apply. Or use traffic lights to show how confident you are (red = ‘I don’t know this’; orange = ‘I’m not very confident about this’; green = ‘I’m confident I can do this’).

Level At the end of the section I can do this

I need more work on this

5 Safely carry out investigations involving distillation and filtration.

5 Describe how distillation and filtration can be used to separate simple mixtures.

5 Recall the melting and boiling points of water, and describe the effects of dissolved impurities of these temperatures.

5 Safely carry out investigations involving dilute acids and alkalis.

5 Identify and explain the meaning of the hazard symbols associated with acids and bases, including those for corrosive, harmful and toxic.

5 Explain the choice of apparatus for investigations such as the neutralisation reaction between acids and alkalis, and the production of a salt.

5 Draw line graphs to present the results of a neutralisation investigation, interpret the data and draw conclusions from them.

5 Use indicators and pH numbers to classify solutions as strongly acidic, weakly acidic, neutral, weakly alkaline and strongly alkaline.

5 Explain how acid rain is caused, and describe some of its effects on the environment.

6 Describe how to control the risks of working with acids and alkalis.

6 Identify the variables involved in an investigation, including the independent variable, the dependent variable and control variables.

6 Describe and explain what happens to pH during a neutralisation reaction.

6 Suggest how to improve an investigation, and give suitable reasons for these suggestions.

3 Water and solutions




6 Explain some common uses of neutralisation reactions.

6 Recall the products formed when acids react with metal hydroxides, metal oxides and metal carbonates.

6 Write word equations for the reactions between some common acids and bases.

6 Recall ways in which the problems of acid rain can be reduced.

7 Describe water in terms of its chemical formula and the elements it contains.

7 Order and describe the main stages in the water cycle.

7 Describe how water from reservoirs is treated so that it becomes safe to drink.

7 Explain the impact on living things of water pollution from farms, factories, sewage and industrial accidents.

7 Link the hazards presented by an acid or alkali to its pH value.

7 Describe and explain the temperature changes observed when water is heated until it boils.

7 Give reasons for and against measures to control emissions of sulphur dioxide.

8 Identify a suitable combination of acid and base to produce a particular salt.

8 Write the chemical formulae of some common acids and bases.

8 Write balanced symbol equations for the reactions between some common acids and bases.

8 Discuss how the work of Joseph Black led to a change in our understanding of reactions involving gases, in particular air and carbon dioxide.

8 Describe how the hazards involved the manufacture of sulphuric acid are controlled to maintain health and safety and to protect the environment.

PROGRESSION3

SECTION

Water and solutions

Name Date Class


Tick the boxes that apply. Or use traffic lights to show how confident you are (red = ‘I don’t know this’; orange = ‘I’m not very confident about this’; green = ‘I’m confident I can do this’).



Safely carry out investigations involving distillation and filtration.

Describe how distillation and filtration can be used to separate simple mixtures.

Recall the melting and boiling points of water, and describe the effects of dissolved impurities of these temperatures.

Safely carry out investigations involving dilute acids and alkalis.

Identify and explain the meaning of the hazard symbols associated with acids and bases, including those for corrosive, harmful and toxic.

Explain the choice of apparatus for investigations such as the neutralisation reaction between acids and alkalis, and the production of a salt.

Draw line graphs to present the results of a neutralisation investigation, interpret the data and draw conclusions from them.

Use indicators and pH numbers to classify solutions as strongly acidic, weakly acidic, neutral, weakly alkaline and strongly alkaline.

Explain how acid rain is caused, and describe some of its effects on the environment.

Describe how to control the risks of working with acids and alkalis.

Identify the variables involved in an investigation, including the independent variable, the dependent variable and control variables.

Describe and explain what happens to pH during a neutralisation reaction.

Suggest how to improve an investigation, and give suitable reasons for these suggestions.

3 Water and solutions




Explain some common uses of neutralisation reactions.

Recall the products formed when acids react with metal hydroxides, metal oxides and metal carbonates.

Write word equations for the reactions between some common acids and bases.

Recall ways in which the problems of acid rain can be reduced.

Describe water in terms of its chemical formula and the elements it contains.

Order and describe the main stages in the water cycle.

Describe how water from reservoirs is treated so that it becomes safe to drink.

Explain the impact on living things of water pollution from farms, factories, sewage and industrial accidents.

Link the hazards presented by an acid or alkali to its pH value.

Describe and explain the temperature changes observed when water is heated until it boils.

Give reasons for and against measures to control emissions of sulphur dioxide.

Identify a suitable combination of acid and base to produce a particular salt.

Write the chemical formulae of some common acids and bases.

Write balanced symbol equations for the reactions between some common acids and bases.

Discuss how the work of Joseph Black led to a change in our understanding of reactions involving gases, in particular air and carbon dioxide.

Describe how the hazards involved the manufacture of sulphuric acid are controlled to maintain health and safety and to protect the environment.

3SECTION

End of section test

Name

H I G H E R

Date Class


1 a) What is meant by the term ’pure water’?

________________________________________________________________ [1] b) Describe one simple chemical test for the presence of water.

________________________________________________________________

________________________________________________________________ [2] c) The graph shows how the temperature of pure ice changes as it is heated

from −5 °C.

i) Which point on the graph (A, C or E) represents liquid water? ___________ [1] ii) What are the temperatures B and D?

Temperature B is ________ °C Temperature D is ________ °C [1]

d) i) What effect does dissolving salt have on the freezing point of water?

___________________________________________________________ [1] ii) What effect does dissolving salt have on the boiling point of water?

_____________________________________________________________ [1] [Total 7]

Page of 41

3 End of section test


2 a) i) Explain how drinking water is chlorinated.

____________________________________________________________ [1] ii) Explain why drinking water is chlorinated.

_____________________________________________________________ [1]

b) Why is there a small amount of residue when tap water is evaporated to dryness but a larger amount after the same volume of sea water is evaporated to dryness?

________________________________________________________________ [1]

c) When some fossil fuels are burned in air, sulphur dioxide is formed. This gas causes ‘acid rain’. Describe one way in which the amount of sulphur dioxide in the air can be reduced.

________________________________________________________________ [1] [Total 4]

3 Nathif investigated several substances to discover their effects on universal indicator.

a) The indicator solution changed from green to orange when mixed with vinegar. i) What does the green colour tell you about the universal indicator solution?

_____________________________________________________________ [1]

ii) What does the colour change tell you about vinegar?

_____________________________________________________________ [1]

b) Sodium hydroxide solution is strongly alkaline. What would be the colour produced when universal indicator is added to sodium hydroxide solution?

________________________________________________________________ [1] [Total 3]



4 Kathryn decided to investigate what happens when an alkali is added to an acid. She put 25 cm3 of acid into a beaker and then added 50 cm3 of alkali, 5 cm3 at a time. She measured the pH of the mixture after each addition of alkali. The table shows Kathryn’s results.

Total volume of alkali added (cm3) pH of the mixture

0 3.0 5 4.2

10 4.6 15 4.9 20 5.4 25 8.6 30 11.7 35 11.9 40 12.0 45 12.1 50 12.2

a) Suggest how Kathryn could measure the pH to the precision shown.

________________________________________________________________ [1] b) Kathryn was concerned that her results might not be reliable.

i) How could she improve the reliability of her results?

___________________________________________________________ [1] ii) How could she check the reliability of her results?

_____________________________________________________________ [1] c) Which is stronger, the acid or the alkali? Explain your answer.

________________________________________________________________

________________________________________________________________ [2] [Total 5]



5 The instructions for preparing dry crystals of a particular salt have become muddled up. a) Write the numbers 2, 3, 4, 5, and 6 in the spaces below to put the instructions in

the correct order. [2]

Step Instructions

1 Put 15 cm3 of dilute sulphuric acid in a test tube

Transfer the filtrate to an evaporating basin

Put the test tube in a hot water bath

Leave the solution so that the water can evaporate

Filter the mixture

Add small portions of copper oxide powder until the mixture stays cloudy

7 Examine the copper sulphate crystals

b) Why must the mixture be filtered?

________________________________________________________________ [1] c) Complete the word equation below:

sulphuric acid + copper oxide → _________________ + _________________ [2] d) Copper oxide is a base. Is it also an alkali? Explain your answer.

________________________________________________________________

________________________________________________________________ [1] [Total 6]

EXTENSION3

SECTION

End of section test

Name Date Class


1 Kathryn put 25 cm3 of acid into a beaker and then added 50 cm3 of alkali, 5 cm3 at a time. She measured the pH of the mixture after each addition of alkali. The table shows her results.

Total volume of alkali added (cm3) pH of the mixture

0 3.0 5 4.2

10 4.6 15 4.9 20 5.4 25 8.6 30 11.7 35 11.9 40 12.0 45 12.1 50 12.2

a) Why did the pH of the mixture increase during the experiment?

________________________________________________________________ [1] b) Which is stronger, the acid or the alkali? Explain your answer.

________________________________________________________________

________________________________________________________________ [2] c) Complete the word equation below:

hydrochloric acid + sodium hydroxide → ______________ + _______________ [2] d) Name the gas given off when acids react with metals.

________________________________________________________________ [1] [Total 6]



2 Potassium nitrate is used in fertilisers. ‘Low salt’ products contain potassium chloride. a) Name the acid needed to produce potassium nitrate.

________________________________________________________________ [1] b) Name a base used to make potassium chloride and potassium nitrate.

________________________________________________________________ [1] c) What happens to an acid when a base is added to it?

________________________________________________________________ [1] [Total 3]

3 The names and chemical formulae of six compounds are shown in the table.

Name Formula Name Formula

ammonia NH3 potassium sulphate K2SO4

ammonium phosphate (NH4)3PO4 phosphoric acid H3PO4

potassium hydroxide NaOH sulphuric acid H2SO4

a) Phosphoric acid reacts with ammonia to form ammonium phosphate. Balance the symbol equation below for the reaction:

H3PO4 + NH3 → (NH4)3PO4 [1] b) Sulphuric acid reacts with potassium hydroxide. Complete and then balance the symbol equation below for the reaction:

H2SO4 + KOH → ______________ + ______________ [3] [Total 4]



4 Hannah wanted to try some of Joseph Black’s experiments from the 18th century. a) She weighed exactly 1.00 g of calcium carbonate, and then heated it strongly for

ten minutes. The symbol equation for the reaction is:

CaCO3 → CaO + CO2 She weighed the residue after it had cooled and found that its mass was 0.56 g.

i) Why did the mass decrease?

_____________________________________________________________ [1] ii) She heated the residue for a second time then let it cool. Why did the mass

stay at 0.56 g when she heated the residue again?

_____________________________________________________________ [1]

b) She weighed another 1.00 g of calcium carbonate, and then mixed it with 10 g of hydrochloric acid. The symbol equation for the reaction is:

CaCO3 + 2HCl → CaCl2 + H2O + CO2 i) Hannah had added enough acid to react with all the solid. What was the total

mass of the solid and acid after the reaction? Show your working out.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________ [2] ii) Explain your answer to part (i)

_____________________________________________________________

_____________________________________________________________ [2] [Total 6]



5 Steve wanted to see if the mass of dissolved salt affects the boiling point of water. a) Write a plan for Steve’s investigation, which uses ordinary laboratory equipment.

Your plan must:

• identify the independent variable and the dependent variable

• identify a control variable

• include a brief description of how to do the experiment. [4]

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________ b) Make a table that Steve could use to record his results in the space below. [2]

[Total 6]

3SECTION

End of section mark scheme


Higher tier (equivalent to NC levels 5 and 6)

Question Answer Mark scheme NC level (optional)

1 a Water with nothing else mixed or dissolved in it

1 mark – or any equivalent answer

5

b Anhydrous copper sulphate crystals turn from white to blue Cobalt chloride paper turns from blue to pink

1 mark for correct substance 1 mark for correct colour change

5

c i C 1 mark 6 ii B is 0 °C; D is 100 °C 1 mark – need

both 6

d i Decreases the freezing point 1 mark 6 ii Increases the boiling point 1 mark 6 2 a i Chlorine gas is bubbled through the water 1 mark 5 ii To kill bacteria / harmful microorganisms 1 mark 5 b Tap water contains a small amount of

dissolved substances; sea water contains a lot of dissolved substances

1 mark – or any equivalent answer

5

c Burn less fossil fuels / remove sulphur from fossil fuels before they are burned / remove sulphur dioxide from flue gases

1 mark 5

3 a i It is neutral / its pH is 7 1 mark 5 ii It is a weak acid / it is weakly acidic 1 mark – must

refer to weak acid 5

b dark blue / purple / violet 1 mark 5 4 a Use a pH meter 1 mark 5 b i Repeat her experiment 1 mark 6 ii Compare her results with another group 1 mark 6 c The alkali

When equal volumes had been mixed, the pH was higher than 7

1 mark 1 mark

6

5 a 5 Transfer ... evaporating basin 2 Put the ... water bath 6 Leave the ... evaporate 4 Filter the mixture 3 Add small ... stays cloudy

2 marks for all steps in correct order 1 mark if three steps are in correct order

6

b To remove unreacted copper oxide 1 mark 6 c copper sulphate; water 1 mark each,

either order 6

d No – it is insoluble in water Answer and reason needed for 1 mark

6

3 End of section mark scheme


Extension tier (equivalent to NC levels 6, 7 and 8)


1 a The alkali neutralised the acid / alkalis have high pH values

1 mark 6

b The alkali When equal volumes of alkali and acid had been mixed, pH was higher than 7

1 mark 1 mark

6

c water sodium chloride

1 mark 1 mark

6

d hydrogen 1 mark 6

2 a nitric acid 1 mark 7

b potassium oxide / potassium hydroxide / potassium carbonate

1 mark 7

c It is neutralised 1 mark 7

3 a H3PO4 + 3NH3 → (NH4)3PO4 1 mark 8

b H2SO4 + 2KOH → K2SO4 + 2H2O or H2SO4 + KOH → KHSO4 + H2O

1 mark for each correct product 1 mark for balancing

8

4 a i Carbon dioxide was given off 1 mark 8

ii All the calcium carbonate had decomposed / calcium oxide does not decompose when it is heated

1 mark 8

b i e.g. 1.00 + 10.00 – 0.44 = 10.56 g

1 mark 1 mark

8

ii Carbon dioxide was lost in both reactions. The same mass of calcium carbonate would release the same mass of gas

1 mark 1 mark

8

5 a Independent variable: mass of salt Dependent variable: boiling point Control variable: volume of water Simple workable method that includes at least three key pieces of apparatus, such as balance, Bunsen burner, measuring cylinder, thermometer. Reference to safety steps taken

1 mark – ½ mark for each variable 1 mark 1 mark 1 mark

7

b Table with columns/rows labelled for mass of salt added and boiling temperature Both headings labelled with units

1 mark 1 mark

7

3SECTION

Question bank

Name Date Class


1 The table shows estimates for the annual amount of evaporation and precipitation (rain, hail and snow) that happens in the Earth’s water cycle.

Over oceans Over the land Evaporation (trillions of tonnes per year) 428 72

Precipitation (trillions of tonnes per year) 391 109

a) Draw a suitable chart to show the information in the table. [2] b) i) Calculate the total annual amount of evaporation in a year. ____________________________________________________________ [1] ii) Calculate the total annual amount of precipitation in a year. _____________________________________________________________ [1]

iii) Compare your answers to parts (i) and (ii). Explain what you notice. _____________________________________________________________ _____________________________________________________________ [1]

c) What is the source of the energy that drives the water cycle? _______________ [1] d) What percentage of total evaporation happens over the oceans? Suggest why

this is so. ___________________________________________________________ ___________________________________________________________ [1]

3 Question bank


e) Explain why the figures in the table are estimates, and may vary according to which team of scientists has worked on the problem.

___________________________________________________________ ___________________________________________________________ ___________________________________________________________ [1]

[Total 8] 2 Abrar found a bottle of a clear, colourless liquid. He thought it was pure water, but its

label was missing. a) Describe what he would see if the liquid was pure water and he added it to:

i) anhydrous copper sulphate crystals _______________________________ [1]

ii) dry cobalt chloride paper ________________________________________ [1]

b) The tests described in part (a) would not prove that the liquid was pure water. Describe a physical test that Abrar should carry out to see if the liquid was pure water. Explain the results he should get for pure water.

______________________________________________________________ ______________________________________________________________ ______________________________________________________________ [3]

[Total 5]

3 Chemists can use indicators to distinguish between acidic, neutral and alkaline solutions. Universal indicator and litmus are not the only indicators. The table shows the colours at different pH values of two other indicators – phenolphthalein and thymol blue.

pH value Indicator 1 2 3 4 5 6 7 8 9 10 11 universal indicator red orange yellow green blue violet

litmus red purple blue

phenolphthalein colourless pink

thymol blue red yellow blue

a) Jenny tested different substances with different indicators. Identify the colours she would see for: i) a neutral solution with litmus ____________________________________ [1]

ii) a strongly alkaline solution with phenolphthalein _____________________ [1]

iii) a weakly acidic solution with thymol blue ___________________________ [1]

3 Question bank


b) Suggest why phenolphthalein is less useful than thymol blue as an indicator when analysing acids.

___________________________________________________________ [1] c) Suggest why universal indicator is used so often compared to the other ones. ___________________________________________________________ ___________________________________________________________ [2]

[Total 6]

4 Stomach acid is hydrochloric acid. One cause of indigestion is the presence of too much of this acid. Antacids are medicines that people can swallow to neutralise some of the stomach acid, and so relieve the symptoms. a) ‘Milk of Magnesia’ is an antacid containing magnesium hydroxide.

i) Write a word equation for the reaction when Milk of Magnesia is swallowed. ___________________________________________________________ [1] ii) Suggest why sodium hydroxide is not used in indigestion remedies. ___________________________________________________________ [1]

b) Some antacids contain calcium carbonate rather than magnesium hydroxide. i) Name the salts formed when these antacids react with hydrochloric acid.

___________________________________________________________ [1] ii) Suggest one side-effect of swallowing an antacid tablet that contains calcium

carbonate. ___________________________________________________________ [1]

iii) Write a balanced symbol equation for the reaction. ___________________________________________________________ [2]

[Total 6]

3SECTION

Question bank mark scheme



1 a Appropriate graph (e.g. bar chart) with sensible scales and labelled axis Bars plotted correctly and identified

1 mark 1 mark

5

b i 428 + 72 = 500 trillion tonnes 1 mark 5 ii 391 + 109 = 500 trillion tonnes 1 mark 5 iii The amounts are the same / the water is being

driven around the water cycle 1 mark (explanation needed)

6

c Heat (thermal) energy from the Sun 1 mark 6 d (428 ÷ 500) × 100 = 85.6 %

Most of the Earth is covered by oceans 1 mark for calculation and reason

7

e Sensible suggestion – e.g. different scientists may use different methods

1 mark 8

2 a i Colour change from white to blue 1 mark (both colours)

5

ii Colour change from blue to pink 1 mark (both colours)

5

b Description of how to measure melting and boiling points of water – e.g. heat ice up, take temperature at regular intervals until boiling Temperatures should be 0 °C and 100 °C

1 mark for sensible method, 1 mark for explaining results 1 mark for both

7

3 a i purple 1 mark 5 ii pink 1 mark 6 iii yellow 1 mark 6 b Thymol blue distinguishes weak acids from

strong ones, unlike phenolphthalein 1 mark 7

c Greater range of colours Greater range of pH values identified

1 mark 1 mark

7

4 a i hydrochloric acid + magnesium hydroxide → magnesium chloride + water

1 mark 6

ii strong alkali / corrosive 1 mark 6 b i calcium chloride 1 mark 6 ii wind, burping 1 mark 7 iii 2HCl + CaCO3 → CaCl2 + H2O + CO2 1 mark for

formulae 1 mark for balancing

8

3SECTION

Answers


Topic 3.1 Quick check questions 1 A – water being heated; particles move about

faster in the liquid; temperature is rising [1] B – water being heated, particles move about as

fast as they can in the liquid; temperature has risen to the boiling point of water [1]

C – water is heated to its boiling point, temperature does not rise anymore; additional energy makes particles leave the liquid and become a gas [1]

D – water being cooled; particles move slower in the liquid; temperature is falling [1]

E – water cooled to its freezing point; the liquid starts to change into a solid as particles start to become fixed in position and don’t move over each other [1]

F – all the water has changed into solid (ice); as it cools further the temperature falls further; particles vibrate slower and slower [1]

2 freezing [1] – ice forming; condensation [1] – clouds forming; evaporation [1] – puddles drying up; [1] for descriptions 3 River water contains germs [1] and solid

particles [1] 4 Rivers in city could contain pollution from

factories and houses, fuels, detergents, etc. River in the countryside could contain pollution from farming, fertilisers, etc. [Any 3]

5 Put some in an evaporating basin and heat it to evaporate the water [1]; any impurities will be left in the evaporating basin [1]

Topic 3.1 Questions 1 Water is a compound of oxygen [½] and

hydrogen [½]. The formula of water is H2O [½] We can test for water by using cobalt chloride

paper which changes from blue [½] to pink [½] Water boils at 100 °C [½] and melts at 0 °C [½].

Impurities raise [½] the boiling point of water. [Total 4] 2 Any suitable phrase to explain words – e.g. a) The water cycle shows the changes of state of

water in nature [1] b) Condensation of water in the upper

atmosphere to form water droplets leads to cloud formation [1] [Total 2]

3 a) 1 Sun [½]; 2 sea [½]; 3 clouds [½]; 4 rain [½]; 5 mountain [½]; 6 snow [½]; 7 river [½]; 8 lake [½] [Total 4]

b) Suitable sentences including words – e.g. i) Condensation occurs in the upper atmosphere

[1] ii) Freezing occurs high up where the

temperatures falls below the freezing point of water [1]

iii) Evaporation occurs when the water in the sea, rivers and lakes is heated and turns into a gas [1]

iv) Melting occurs as the snow and ice is heated and turns into a liquid [1] [Total 8]

4 a) reservoir [1] b) filtration [1] c) chlorine [1] [Total 3] 5 Labelled diagram including evaporating basin ½]; tripod stand [½]; Bunsen burner [½]; tap water ½] [Total 2] 6 a) Title [1]; labels on axes [1 ]; scale and

units/names on each axis [1 ]; accurately drawn [1]

b) Washing ourselves [1] c) 160 litres [1] d) 25% [1] [Total 7] 7 Each source [4 × ½]; each threat [4 × ½] [Total 4] 8 sodium chloride; magnesium; calcium;

potassium; iodine etc. [½ each max. 2] [Total 2] Topic 3.2 Quick check questions 1 Substance that changes colour depending on the

type of solution [1] 2 It can damage skin and metals [1] 3 a) blue/purple [1] b) red/orange [1] c) green [1] d) blue/purple [1] 4 Orange juice is already coloured [1] 5 Rises towards 7 [1] 6 From red to orange to yellow to green [1] Topic 3.2 Questions 1 Acids have a pH that is less [½] than 7 and turn

universal indicator orange [½] or red [½]. Alkalis have a pH that is more [½] than 7 and

turn universal indicator blue [½] or purple [½] [Total 3] 2 One suitable sentence for each of the following

words – e.g. a) Neutralisation occurs when an acid cancels

out an alkali to form a neutral solution [1] b) Solution with a pH less than 7 is an acid [1] c) An indicator changes colour in acids and

alkalis [1] d) The pH scale is a measure of how acid or

alkaline a solution is [1] [Total 4] 3 a) E [1] b) D [1] c) A [1] d) A, B and C [2] [Total 5] 4 E.g. The nettle sting is acidic so rubbing with an

alkali [1] will neutralise [1] the acid [1] and relieve the sting [Total 3]

5 a) Measure volume of acid [½] using syringe [½] etc. into beaker. Add indicator [½]. Add acid [½]

3 Answers


using syringe [½] etc. until indicator shows neutral [½]

b) Indicator would go green [1] c) Wear safety glasses [1] and wash any

splashes immediately [1] d) 25 cm3 [1] [Total 7] Topic 3.3 Quick check questions 1 salt and water are formed [1] 2 Dissolved in the water [1] 3 By using an indicator [1] and adding the acid

slowly until the indicator shows the solution is neutral [1]

4 nitric acid + sodium hydroxide → sodium nitrate + water [2]

5 a) nitric acid + lead oxide → lead nitrate + water [2] b) sulphuric acid + sodium carbonate → sodium

sulphate+ water + carbon dioxide [2] 6 Substance which neutralises an acid forming a

salt and water [1] 7 A base can be soluble or insoluble in water – an

alkali is soluble in water [1] 8 Contains dissolved carbon dioxide [1] Topic 3.3 Questions 1 When an acid [½] reacts with a base we say a

neutralisation [½] reaction has occurred. Neutralisation reactions always produce a salt

[½] and water [½] [Total 2] 2 a) sulphuric acid [1] b) hydrochloric acid [1] c) nitric acid [1] [Total 3] 3 Hydrogen [1]; lighted splint [1] pops [1] Carbon dioxide [1]; limewater [1] goes milky [1] [Total 6] 4 Suitable sentence containing each pair of words a) An acid reacts with a metal oxide [1] to form a

salt and water [1] b) An acid reacts with a metal carbonate [1] to

form a salt, carbon dioxide and water [1] [Total 4] 5 a) sulphuric acid + magnesium → magnesium

sulphate [1] + hydrogen [1] b) nitric acid [1] + potassium hydroxide →

potassium nitrate + water [1] c) copper carbonate + hydrochloric acid →

copper chloride [1] + water [1] + carbon dioxide [1]

d) zinc oxide [1] + phosphoric acid [1] → zinc phosphate + water [Total 9]

6 a) cobalt oxide/hydroxide/carbonate [1] + hydrochloric acid [1]

b) iron oxide/hydroxide/carbonate [1] + sulphuric acid [1]

c) zinc oxide/hydroxide/carbonate [1] + nitric acid [1] [Total 6]

7 Each word in correct context – e.g. When an acid [1] reacts with an alkali [1] the

main product [1] is a salt [1] [Total 4] 8 a) Less air pollution (from burning fuels) [1] b) An alkali [1] c) No – it will always contain some carbon

dioxide from our atmosphere [1] [Total 3] 9 a) carbon dioxide [1] b) Stops fizzing [1] c) zinc chloride [1] d) effervescence [1]; neutralisation [1] e) filter funnel [½]; filter paper [½]; name the

residue [½]] and filtrate [½] [Total 7] 10 Put small amount of each in different test tubes. Add a piece of magnesium to each. The one that fizzes is hydrochloric acid [2] Wash out the test tubes and put some of the two

unknown solutions in different test tubes. Add some hydrochloric acid to each. The one that fizzes is potassium carbonate. [2] The other is sodium hydroxide. [2] You should wear safety glasses and wash spills

with water [1] [Total 7] HSW Topic 3.4 The scientific method Quick check questions 1 An educated guess at an answer to a question

[1] 2 An idea about why things happens – it tries to

explain the facts [2] 3 Heating magnesia alba [1]; adding sulphuric acid

to magnesia alba[1]; the manufacture of alcohol[1]; burning charcoal[1]; and by respiration[1]

Questions 1 Hypothesis – educated guess based on

experiences in other areas [2] Conclusion – description of what happens based

on observations made during experiments [2] [Total 4] 2 a) He presented a lecture to the Philosophical

Society of Edinburgh [1] b) He might have use video conferencing or

published on the internet [2] c) Other scientists would carry out experiments

to see if they could get the same results [2] [Total 5] 3 a) Priestley and Lavoisier [2] b) Importance of careful measurement [1] [Total 3] 4 a) calcium carbonate → calcium oxide + carbon

dioxide [2 − ½ each mistake] b) calcium oxide + carbon dioxide → calcium

carbonate [2 − ½ each mistake] [Total 4] 5 Labelled diagram showing flask [1] containing

magnesium carbonate and sulphuric acid[1],

3 Answers


delivery tube to trough [1] with upturned test tube full of water[1] and gas bubbling into test tube [1]

[Total 5] 6 Thinking about a question [1] Research into the problem [1] Planning and carrying out experiments [1] Analysing the results [1] Making the results and conclusions available to

other scientists [1] [Total 5] HSW Topic 3.4 The chemical industry Quick check questions 1 It improves our standards of living, creates

wealth (exports) and creates jobs [2] 2 Health and safety (control of hazardous

substances) [1]; the effect on the local environment [1]

3 fertilisers [1] 4 Control of Substances Hazardous to Health [1] Questions 1 a) The Contact process [1]; sulphur [1], air [1],

water [1] b) sulphur + oxygen [1] → sulphur dioxide [1] sulphur dioxide + oxygen [1] sulphur trioxide

[1] [Total 8] 2 a) 98% [2] b) wear eye protection [1]; gloves [1]; keep away

from mouth [1]; it is corrosive and toxic [1] [Total 6] 3 a) Availability of trained workers [1]; availability

of water [1]; sulphur distance to markets [1]; pollution of local area [1]; safety procedures for workforce [1]

b) employment [1]; associated industries [1] c) Possible pollution problems [1]; increased

traffic on roads [1] [Total 9] 4 Any five of labourers, cleaners, store men, plant

operators, chemists, lorry drivers, office staff, sales, marketing community liaison, etc. [Total 5]

5 Labels on each axis [1]; scale and units/names on each axis [1]; accurately drawn [1] [Total 3]

End of Section 3 questions 1 a) [1]; H2O [1]

Page of 53

b) ½ mark for each of the following terms

correctly used: Sun; heat; evaporation; higher; cools; condensation; water; droplets; cloud [4]

[Total 6] 2 Add indicator [½]; red/orange acid [1]; green

neutral [½]; blue purple alkali [1] [Total 3] 3 a) 19500 million litres [1] b) 336.2 litres [1]

c) 585 million litres [1] d) 10500 [1] e) flushing toilets [½] and washing [½] [Total 5] 4 They could use presentations at conferences,

articles in magazines or the internet [3] They need to communicate their findings so that

others can check their results and conclusions [1] [Total 4]

5 nitric acid at pH < 2 [1]; bleach ~ 5 [1]; sugar = 7 [1]; sodium hydroxide >12 [1] [Total 4] 6 Acids Alkalis Neutrals [1] vinegar bleach salt orange juice toothpaste sugar tea oven cleaner alcohol battery fluid water indig. remedies [2] [2] [2] [Total 7] 7 a) rises [1] b) falls[1] c) rises[1] d) stays the same [1] [Total 4] 8 a) magnesium + ethanoic acid [1] → magnesium

ethanoate + hydrogen [1] b) sodium carbonate + ethanoic acid [1] →

sodium ethanoate + water + carbon dioxide [1] c) iron oxide + ethanoic acid [1] → iron

ethanoate + water [1] [Total 6] 9 a) sulphuric acid + sodium hydroxide → sodium

sulphate [1] + water [1] b) nitric acid [1] + magnesium [1] → magnesium

nitrate + hydrogen c) zinc oxide + hydrochloric acid [1] → zinc

chloride + water [1] d) phosphoric acid + sodium carbonate →

sodium phosphate [1] + water [1] + carbon dioxide [1] [Total 9]

10 Bicarbonate alkaline [1]; for acidic bee stings [1] Vinegar acidic [1]; for alkaline wasp stings [1] [Total 4] 11 Add excess [½] nickel carbonate [1] to

hydrochloric acid [1] Filter [1] the excess nickel carbonate [½] evaporate [½] half of the water [½] Leave to evaporate [½] to form nickel chloride

crystals [½] [Total 6] 12 a) acidic [1] b) neutralisation [1] c) salt [1] d) calcium carbonate [1] [Total 4]

3 Answers


Topic worksheets 3.1 Our water supply 1 Suitably labelled flow chart including (screen) [1];

settling [1]; filtering [1]; chlorination [1]; storage [1]; piping [1]; with appropriate text

2 a) Bar chart [1]; sensible scales [1]; labelled axes [1]; correctly plotted [1]

b) i) Food preparation and drinking [1] Because it is swallowed [1] ii) flushing toilet, garden, car [1] Water is not swallowed [1] iii) bath, shower, dishwasher, laundry [1] Water might be swallowed or in contact with skin

[1] c) i) Stage identified [1]; sensible reasons [1] ii) Two or more sensible suggestions – e.g.

limited resource, reduction in energy or chemicals [2]

3.2 Answers – not questions Pupil’s own suggestions – 1 mark for each sensible correct question per answer 3.3 Making salts 1 Jigsaws assembled correctly, 1 mark each [8] 2 1 mark for each correct word equation [12] HSW worksheets Chlorination of drinking water 1 a) hydrochloric acid [1]; chloric acid [1] b) chloric acid [1] c) Low pH values ensure a higher concentration

of chloric acid [1] d) Lower pH might be harmful / pH 7.3 is close to

neutral [1] 2 a) Any sensible answer – e.g. it is enough to kill

microorganisms [1] b) i) It is just a bit less than concentration at

which consumers complain [1] ii) Sensible reasons explained – e.g. chlorine is a

gas so it will escape [1]; chlorine reacts with other chemicals in water so amount is reduced [1]

c) Sensible reason explained – e.g. need to be sure that microorganisms are killed [1]; people are not going to drink it [1]

3 Benefits outweigh the risk [1]. Discussion (to a maximum of 3 marks) should include sensible advantages (e.g. makes water safe to drink) and sensible disadvantages (e.g. taste, smell, cost of adding chlorine, etc.) [3]

Joseph Black and chalk 1 a) i) calcium chloride [1]; water [1]; carbon

dioxide [1] ii) carbon dioxide [1] iii) calcium chloride [1]; water [1] b) He needed to make very accurate / precise

measurements to detect small changes in mass [1]

c) Chalk is calcium carbonate [1]; quicklime is calcium oxide [1]

2 a) To make it a fair test [1] b) 1 mark for each of two sensible suggestions –

e.g. he got the same loss in mass in both experiments / the loss in Experiment 1 was caused by a gas (because of fizzing) / there was no further loss of mass in Experiment 3 after the gas had gone [2]

3 a) (Many) people breathed out carbon dioxide [1]; turns limewater cloudy [1]

b) To check if it was something the people produced that made the limewater go cloudy [1]

Sulphuric acid 1 a) £150 per tonne / 4 times [1] b) fertiliser manufacture [1]; bioethanol [1] 2 a) + oxygen [1] b) Sulphuric acid is made from sulphur [1] c) Any two sensible reasons for 1 mark each –

e.g. cost of extraction, cost of transporting it, increased demand, limited supplies, etc. [2]

3 a) Sugar beet must be grown, it needs fertilisers [1]

b) Sulphuric acid is used in the manufacture of fertilisers [1]; an increase in demand for fertilisers increases demand for sulphuric acid [1]

c) Increase in demand for fertilisers [1]; increase in demand for sulphuric acid for bioethanol manufacture [2]

4 1 mark for a sensible reason – e.g. increased price of sulphuric acid means that recycling seems relatively less expensive [1]

1 mark for each suggestion to a maximum of 3: advantages – e.g. saves resources, saves energy; disadvantages – e.g. cost of collection or transport, disposal of waste materials, etc. [3]

3 Answers


Extension worksheets Symbol equations 1 1 mark for each correct name and formula [11] Bases

Acids sodium hydroxide NaOH

copper oxide CuO

magnesium carbonate MgCO3

hydrochl-oric acid HCl

sodium chloride NaCl

copper chloride CuCl2

nitric acid HNO3

sodium nitrate NaNO3

copper nitrate Cu(NO3)2

magnesium nitrate Mg(NO3)2

sulphuric acid H2SO4

sodium sulphate Na2SO4

copper sulphate CuSO4

magnesium sulphate MgSO4

phosph-oric acid H3PO4

sodium phosphate Na3PO4

copper phosphate Cu3(PO4)2

magnesium phosphate Mg(PO)4

2 a) hydrochloric acid + sodium hydroxide →

sodium chloride + water [1] hydrochloric acid + copper oxide → copper

chloride + water [1] nitric acid + sodium hydroxide → sodium nitrate

+ water [1] nitric acid + copper oxide → copper nitrate +

water [1] nitric acid + magnesium carbonate → magnesium nitrate + water + carbon dioxide [1] sulphuric acid + sodium hydroxide → sodium

sulphate + water [1] sulphuric acid + copper oxide → copper sulphate

+ water [1] sulphuric acid + magnesium carbonate →

magnesium sulphate + water + carbon dioxide [1]

phosphoric acid + sodium hydroxide → sodium phosphate + water [1]

phosphoric acid + copper oxide → copper phosphate + water [1]

phosphoric acid + magnesium carbonate → magnesium phosphate + water + carbon dioxide [1]

b) 1 mark for each equation for correctly writing in formulae (see part c) [11]

c) HCl + NaOH → NaCl + H2O [1] 2HCl + CuO → CuCl2 + H2O [1] HNO3 + NaOH → NaNO3 + H2O [1] 2HNO3 + CuO → Cu(NO3)2 + H2O [1] 2HNO3 + MgCO3 → Mg(NO3)2 + H2O + CO2 [1] H2SO4 + 2NaOH → Na2SO4 + 2H2O [1] H2SO4 + CuO → CuSO4 + H2O [1] H2SO4 + MgCO3 → MgSO4 + H2O + CO2 [1] H3PO4 + 3NaOH → Na3PO4 + 3H2O [1] 2H3PO4 + 3CuO → Cu3(PO4)2 + 3H2O [1]

2H3PO4 + 3MgCO3 → Mg3(PO4)2 + 3H2O + 3CO2 [1]

The nature of acids 1 a) 2H2 + O2 → 2H2O [1] b) hydrogen [1] c) i) Dew formed [1] ii) 1 mark for correct substance and 1 mark for

correct colour change – e.g. white anhydrous copper sulphate [1] turns blue [1] / blue cobalt chloride paper turns pink

2 a) oxygen [1] b) i) hydrochloric acid [1] ii) No [1] iii) He made it from sodium chloride, which is

found in sea water [1] 3 a) All three produced acids containing oxygen [1] b) i) hydrogen [1] ii) water [1] iii) water is not an acid (it is neutral) [1]; this is an

exception to his idea [1] 4 a) He was the first person to make it [1] b) He might have said that acids contain

hydrogen [1]; Davy showed that hydrochloric acid did not contain oxygen [1]

c) They contain H for hydrogen [1] d) No – it came from acids [1] e) Oxygen does not always form acids, but acids

contain hydrogen [1]

section the freezing point of water 3 - pearson … salt, on the freezing point of water. page of 2...

Documents